1. Field of the Invention
The invention relates to methods for managing state information associated with user agents in systems utilizing the wireless application protocol. Especially, the invention is related to such a method as specified in the preamble of the independent method claim.
2. Description of Related Art
The following terms and acronyms will be used throughout the application:                WAP Wireless Application Protocol        HTTP Hypertext Transfer Protocol        WML Wireless Markup Language        Client a device or a software application that initiates a request for a connection with a server        Cookie Proxy an intermediate program that acts as a user agent for the purpose of managing cookies and cookie storage on behalf of other user agents        Origin Server the server, on which a given resource resides or is to be created, often referred to as a web server or an HTTP server        Proxy an intermediate program that acts as both a server and a client for the purpose of making requests on behalf of other clients        User a person, who interacts with a user agent to view, hear or otherwise use a resource        User Agent a user agent is any software or device that interprets WML, WMLScript or other content        
On the World Wide Web, the HTTP State Management mechanism stores state information in a file known as a cookie on the client This mechanism is defined in RFC2109. The same mechanism can also be used over the WAP protocols, since HTTP headers are used to convey all state and state manipulation information. RFC2109 defines a means whereby an origin server can request that a small unit of state information i.e. a cookie is stored in the user agent, and included in subsequent requests to the origin server. A variety of controls are available to the origin server, allowing it to control when the cookie is included in subsequent requests, when the cookie expires as well as other state management and transport controls. According to RFC2109 the user agent is responsible for cookie management.
According to the draft specifications for WAP HTTP state management at the time of writing this patent application, a cookie proxy can be used to store manage cookies on behalf of the user agent. Such an approach is described in the patent application WO 99/64967, for example. The advantage of such an approach is the saving of memory capacity and processing capacity in a mobile communication device, and also to save the resources of the air interface. The cookie proxy is an HTTP proxy or proxy equivalent such as a WAP Gateway that manages cookies on behalf of WAP user agents that do not implement the HTTP state function directly. The cookie proxy is responsible for managing and storing cookies on behalf of the user agents, and modifies HTTP requests and responses to and from the user agent to implement this function. However, the cookie proxy concept has a problem, which has not been solved previously. According to RFC2109, some cookies may be bound to the user agent session. Because of this, there should be a method for the cookie proxy to detect when a new session is activated and cookies bound to the previous session should be discarded. This means that the user agent and the cookie proxy must be somehow synchronized. However, the specification drafts existing at the time of writing of this patent application do not specify any ways to remedy this problem.